U.S. patent number 7,166,341 [Application Number 10/762,175] was granted by the patent office on 2007-01-23 for hot melt adhesives based on graft copolymers.
This patent grant is currently assigned to Henkel Kommanditgesellschaft auf Aktien (Henkel KGAA). Invention is credited to Ingo Gensch, Marcus Heemann, Wolfgang Klingberg, Thomas Moeller.
United States Patent |
7,166,341 |
Heemann , et al. |
January 23, 2007 |
Hot melt adhesives based on graft copolymers
Abstract
Water-soluble or water-dispersible hotmelt adhesives are
prepared using graft copolymers produced by graft copolymerizing
olefinically unsaturated monomers onto polyalkylene oxides. The
adhesives additionally contain at least one resin which improves
tackiness and the compatibility of the adhesive components. Other
components such as polymers, plasticizers, and additives may also
be present. The adhesives are especially suited for use in the
labelling of recyclable or reuseable hollow containers. The
adhesive may be completely separated from the hollow containers and
dissolved in an alkaline washing liquor even at low
temperatures.
Inventors: |
Heemann; Marcus (Neuss,
DE), Moeller; Thomas (Duesseldorf, DE),
Gensch; Ingo (Gangelt, DE), Klingberg; Wolfgang
(Korschenbroich, DE) |
Assignee: |
Henkel Kommanditgesellschaft auf
Aktien (Henkel KGAA) (Duesseldorf, DE)
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Family
ID: |
7693035 |
Appl.
No.: |
10/762,175 |
Filed: |
January 21, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040159394 A1 |
Aug 19, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/EP02/07880 |
Jul 16, 2002 |
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Foreign Application Priority Data
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Jul 25, 2001 [DE] |
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101 36 212 |
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Current U.S.
Class: |
428/34.1;
428/34.2; 428/35.7; 428/411.1; 428/500; 525/57; 525/63 |
Current CPC
Class: |
C08F
283/06 (20130101); C09J 151/08 (20130101); Y10T
428/31855 (20150401); Y10T 428/31504 (20150401); Y10T
428/1352 (20150115); Y10T 156/1028 (20150115); Y10T
428/28 (20150115); Y10T 428/1303 (20150115); Y10T
428/13 (20150115) |
Current International
Class: |
C08L
51/08 (20060101); B32B 7/12 (20060101) |
Field of
Search: |
;525/67,57,63
;428/34.1,34.2,35.7,411.1,500 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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692 26 395 |
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Apr 1999 |
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DE |
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0 737 233 |
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Feb 1998 |
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EP |
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0 512 250 |
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Jul 1998 |
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EP |
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WO 95/29952 |
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Nov 1995 |
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WO |
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WO 97/01483 |
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Jan 1997 |
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WO |
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WO 01/48045 |
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Jul 2001 |
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WO |
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Other References
Standard Test Method for Apparent Viscosity of Hot Melt Adhesives
and Coating Materials, American Society for Testing and Materials,
ASTM D 3236-88, pp. 1-8 (1999). cited by other.
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Primary Examiner: Mullis; Jeffrey
Attorney, Agent or Firm: Woodcock Washburn LLP
Parent Case Text
This application is a continuation under 35 USC Sections 365(c) and
120 of International Application No. PCT/EP02/07880, filed 16 Jul.
2002 and published 6 Feb. 2003 as WO 03/010256, which claims
priority from German Application No. 10136212.9, filed 25 Jul.
2001, each of which is incorporated herein by reference in its
entirety.
Claims
What is claimed is:
1. A water-soluble or water-dispersible hotmelt adhesive
comprising: A) 20 to 80% by weight of at least one component (A),
B) 1 to 70% by weight of at least one polymer selected from the
group consisting of polyesters, polyurethanes, alkyl
poly(meth)acrylates, acrylic acid homopolymers, acrylic acid
copolymers and vinyl polymers as component (B), C) 10 to 70% by
weight of at least one resin as component (C) that is different
from said at least one polymer of component (B), said resin
comprising styrene/acrylic acid copolymer, D) 0 to 30% by weight of
at least one plasticizer as component (D), E) 0 to 3% by weight of
at least one additive as component (E), the sum total of components
(A) to (E) being 100% by weight and component (A) being a graft
copolymer containing: i) 30 to 90% by weight olefinically
unsaturated monomer, wherein said olefinically unsaturated monomer
corresponds to one or more monomers selected from (i-a) at least
one olefinically unsaturated monomer selected from the group
consisting of a) mono- and di-esters of crotonic acid, cinnamic
acid, fumaric acid, maleic acid, citraconic acid, and itaconic
acid; b) carboxyfunctional monomers; c) N-vinyl caprolactam, vinyl
phosphonates, N-vinyl formamides, N-vinyl acetamides, hydroxypropyl
acrylates and methacrylates, monoacrylates and monomethacrylates of
polyalkylene glycols, acrylates, methacrylates, acrylic acid and
methacrylic acid amides containing amine groups; d) vinyl esters
corresponding to general formula (I)
CH.sub.2.dbd.CH----O----C(O)----R.sub.1, with R.sub.1=C.sub.11-21,
(I) the at least one olefinically unsaturated monomer of group (a),
(b), (c) or (d) being present in the graft copolymer in a quantity
of up to 50% by weight; or (i-b) a mixture of olefinically
unsaturated monomers of vinyl acetate and, based on the graft
copolymer, up to 50% by weight of at least one olefinically
unsaturated monomer selected from the group consisting of stearyl
acrylate, vinyl laurate, vinyl versatate, lauryl acrylate, lauryl
methacrylate, dibutyl maleate, dibutyl itaconate, dibutyl fumarate
and acrylates and methacrylates corresponding to general formula
(II): CH.sub.2.dbd.CR.sub.2----C(O)----O----R.sub.3 with R.sub.2=H
or CH.sub.3 and R.sub.3=C.sub.12-22; (II) or (i-c) at least one
monomer selected from the group consisting of vinyl acetate and
vinyl propionate; and ii) 10 to 70% by weight of polyalkylene oxide
where the ethylene oxide content of the polyalkylene oxide is at
least 50% by weight.
2. A hotmelt adhesive as claimed in claim 1, wherein the
olefinically unsaturated monomer corresponds to group (i-a) and
contains at least one olefinically unsaturated monomer selected
from the group consisting of acrylates and methacrylates
corresponding to general formula (II):
CH.sub.2.dbd.CR.sub.2----C(O)----O----R.sub.3 with R.sub.2=H or
CH.sub.3 and R.sub.3=C.sub.12-22 (II).
3. A hotmelt adhesive as claimed in claim 1, wherein the ethylene
oxide content of the graft copolymer is at least 75% by weight.
4. A hotmelt adhesive as claimed in claim 1 having a Brookfield
viscosity at 150.degree. C. of 200 mPas to 2,500 mPas, as measured
by ASTM D 3236-88.
5. A hotmelt adhesive as claimed in claim 1, wherein the
polyalkylene oxides are selected from the group consisting of
homopolymers of ethylene oxide, block copolymers of ethylene oxide
and propylene oxide, statistical copolymers of ethylene oxide and
propylene oxide, ether-terminated homopolymers of ethylene oxide,
ester-terminated homopolymers of ethylene oxide, ether-terminated
block copolymers of ethylene oxide and propylene oxide,
ester-terminated block copolymers of ethylene oxide and propylene
oxide, ether-terminated statistical copolymers of ethylene oxide
and propylene oxide, and ester-terminated statistical copolymers of
ethylene oxide and propylene oxide.
6. A hotmelt adhesive as claimed in claim 1, wherein the
polyalkylene oxide is a mixture of at least one high molecular
weight polyalkylene oxide and at least one low molecular weight
polyalkylene oxide, said mixture having a Brookfield melt viscosity
of 100 mPas to 80,000 mPas at 100.degree. C., as measured by ASTM D
3236-88.
7. A hotmelt adhesive as claimed in claim 1 wherein the graft
copolymer is comprised of 60 to 80% by weight olefinically
unsaturated monomer.
8. A hot melt adhesive as claimed in claim 1, wherein component (B)
is comprised of at least one of: B1) 10 to 50% by weight, based on
the weight of the hotmelt adhesive, of at least one (meth)acrylic
acid polymer; B2) 5 to 30% by weight, based on the weight of the
hotmelt adhesive, of at least one polyester; B3) at least one alkyl
poly(meth)acrylate, the alkyl group having a chain length of 1 to
18 carbon atoms; B4) at least one polyvinyl alcohol; B5) at least
one polyvinyl alkylether containing 1 to 14 carbon atoms in the
alkyl group; or B6) 5 to 30% by weight of at least one
polyurethane.
9. A hotmelt adhesive as claimed in claim 1, wherein component (B)
comprises a polyester based on aromatic dicarboxylic acids
containing sulfo groups.
10. A hotmelt adhesive as claimed in claim 1, wherein component (C)
additionally comprises at least one resin selected from the group
consisting of a) hydroabietyl alcohol and esters thereof; b)
natural resins and modified natural resins; c) copolymers of
styrene and maleic anhydride; d) acrylic acid copolymers other than
styrene/acrylic acid copolymers; e) resins based on functional
hydrocarbon resins; and (f) alkyl esters of partly hydrogenated
rosins.
11. A hotmelt adhesive as claimed in claim 1, comprising: A) 20 to
80% by weight of component (A); B) 5 to 20% by weight of at least
one polyester as component (B2); C) 10 to 70% by weight of at least
one styrene/acrylic acid copolymer as component (C); D) 5 to 25% by
weight of at least one plasticizer based on polyalkylene glycol
with a molecular weight of 200 to 6,000 g/mol as component (D); the
sum total of the components being 100% by weight.
12. An article of manufacture comprising a hotmelt adhesive as
claimed in claim 1 and a substrate.
13. An article of manufacture as claimed in claim 12, wherein said
article of manufacture is selected from the group consisting of
hollow containers, books, boxes, and sanitary articles.
14. An article of manufacture as claimed in claim 12, wherein said
substrate is comprised of plastic.
15. An article of manufacture as claimed in claim 12, comprising
said hotmelt adhesive, a hollow container, and a label wherein said
label is bonded to said hollow container using said hotmelt
adhesive.
Description
FIELD OF THE INVENTION
This invention relates to a water-soluble or water-dispersible
hotmelt adhesive based on graft copolymers, to its production and
to its use for labelling recyclable or reusable hollow
containers.
DISCUSSION OF THE RELATED ART
Hotmelt adhesives are adhesives which are applied as a melt to the
substrates to be bonded and, after the substrates have been fitted
together, set by solidifying on cooling.
Both pressure-sensitive adhesive systems and non-blocking
granulatable adhesive systems are available are on the market.
Hotmelt adhesives based on graft copolymers are known. U.S. Pat.
No. 3,891,584 describes a water-dispersible hotmelt adhesive
containing 75 to 95 parts of a graft copolymer of about 40 to 80%
vinyl monomer and about 20 to 60% by weight water-soluble
polyalkylene oxide polymer and 5 to 25% by weight tackifying resin.
The vinyl monomer is preferably vinyl acetate or low molecular
weight alkyl-substituted acrylate. This hotmelt adhesive is used
inter alia for labeling returnable bottles at high speeds. The
labels can be removed by brief soaking in hot water.
DE 69226395 T2 describes a process for bonding non-woven textile
substrates to similar or different substrates which comprises
applying a molten hotmelt adhesive composition containing A. 50 to
100% by weight of a graft copolymer and B. 0 to 50% by weight of a
tackifying resin to at least one substrate. The graft copolymer
comprises a) 40 to 85% by weight of at least one vinyl monomer, b)
15 to 60% by weight of at least one polyalkylene oxide polymer with
a molecular weight of more than 3,000 and a content of at least 50%
by weight polymerized ethylene oxide. The adhesive has a T.sub.g of
-40 to 40.degree. C.
Hotmelt adhesives for labeling recyclable hollow containers are
known. WO 97/01483 describes an adhesive system for bonding
wrap-around labels which comprises a pickup adhesive and an overlap
adhesive. If the pickup adhesive is to remain on the container and
not on the label, it should preferably be alkali-soluble. An
alkali-soluble pickup adhesive such as this contains I. 20 to 58%
by weight of at least one alkali-soluble polymer which serves as a
backbone polymer, II. 1 to 70% by weight of at least one resin
based on functional hydrocarbon resins or optionally modified
natural resins, III. 0.5 to 30% by weight of at least one
plasticizer and IV. 0 to 3% by weight of at least one typical
auxiliary and additive.
According to Example B), this adhesive dissolves completely in a 1%
caustic soda solution in 2 to 10 minutes at 80.degree. C. The
advantage of this known adhesive is that the plastic containers or
parts thereof are adhesive-free after the alkali wash and can be
reused either directly or in the production of new containers.
However, the described systems have room for improvement. Where
they are processed in high-performance labeling machines, but also
when it comes to storage of labeled hollow containers which have
been produced using the described adhesive systems, improvement,
particularly in regard to cohesion, appears to be necessary.
Against the background of this prior art, the problem addressed by
the present invention was to provide a water-soluble or
water-dispersible hotmelt adhesive which would enable
adhesive-containing products to be re-used in a simple,
environmentally friendly and economic manner. The original positive
application and performance properties of the hotmelt adhesive
would, of course, remain unaffected.
Another problem addressed by the present invention was to provide a
water-soluble or water-dispersible hotmelt adhesive which would
have high inner strength (cohesion). This is necessary in order to
guarantee smooth machine operation, particularly in the case of
high-speed labeling machines, or prolonged storage of labeled
hollow containers, more particularly hollow containers filled with
liquids containing carbon dioxide.
Another problem addressed by the invention was to provide a
water-soluble or water-dispersible hotmelt adhesive which could be
applied at low temperatures.
Another problem addressed by the invention was to provide a
water-soluble or water-dispersible hotmelt adhesive for hollow
containers of recyclable material which would have high resistance
to frozen water or condensation.
Another problem addressed by the invention was to provide a process
for the production of a water-soluble or water-dispersible hotmelt
adhesive having the properties mentioned above.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a water-soluble or water-dispersible
hotmelt adhesive based on at least one water-soluble,
water-dispersible or alkali-soluble polymer prepared by graft
copolymerization of olefinically unsaturated monomers onto
polyalkylene oxides as component (A), characterized in that the
hotmelt adhesive contains A) 20 to 80% by weight of component (A),
B) 0 to 70% by weight of at least one polymer from the group of
polyesters, polyurethanes, alkyl poly(meth)acrylates, acrylic acid
homopolymers and/or copolymers and/or vinyl polymers, C) 10 to 70%
by weight of at least one resin, D) 0 to 30% by weight of at least
one plasticizer, E) 0 to 3% by weight of at least one typical
auxiliary and additive, the sum total of the components being 100%
by weight.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION
The graft copolymers--component (A)--used in accordance with the
invention are water-soluble, water-dispersible or alkali-soluble
polymers which are prepared by graft copolymerization of
olefinically unsaturated monomers onto polyalkylene oxides. Such
graft copolymers are described, for example, in U.S. Pat. No.
3,891,584.
The polyalkylene oxides are preferably selected from the group of
homopolymers of ethylene oxide, block copolymers of ethylene oxide
(EO) and propylene oxide (PO), statistical copolymers of ethylene
oxide (EO) and propylene oxide (PO) and are used individually or in
the form of mixtures. The corresponding derivatives with esterified
or etherified terminal groups are also suitable. Commercially
available derivatives are, for example, polyglycols of the M and
P41 (Clariant) series, such as triethylene glycol dimethylether,
polyethylene glycol dimethylether, polyethylene glycol
dibutylether, polyethylene glycol monoallylether, polyethylene
glycol allylmethylether, polyethylene glycol diallylether and
polyalkylene glycol monoallylether and polyalkylene glycol
allylmethylether. Polyalkylene oxides mono- and di-esterified with
fatty acids, more particularly esters based on caprylic acid,
capric acid, lauric acid, myristic acid, palmitic acid, stearic
acid, behenic acid, coconut fatty acid, palm kernel oil fatty acid
or tallow fatty acid, as marketed for example by Cognis, are also
used.
Commercially available EO/PO block copolymers are, for example, the
copolymers sold under the PLURONIC trade name by BASF; commercially
available statistical EO/PO copolymers are, for example, the
copolymers sold under the trade name BREOX by International
Speciality Chemicals. Statistical or block copolymers of ethylene
oxide with other alkylene oxides, for example butylene oxide, are
also suitable.
The polyalkylene oxides have a molecular weight of 400 to 50,000
g/mol, preferably in the range from 1,500 to 35,000 g/mol and more
particularly in the range from 3,000 to 20,000 g/mol.
Combinations of high molecular weight polyalkylene oxides with low
molecular weight polyalkylene oxides are particularly advantageous.
Examples include mixtures of PEG 35000 with PEG 600, PEG 20000 with
PEG 600 or PEG 12000 with PEG 600. Accordingly, even very high
molecular weight polyalkylene oxides, which cannot be processed on
their own because of their high melt viscosities, can be grafted by
the processes described in the following.
Accordingly, only in such combinations is it also possible to use
polyalkylene oxides with molecular weights above the 50,000 g/mol
mentioned above. Corresponding polyalkylene oxide mixtures have
Brookfield melt viscosities of 100 mPas to 80,000 mPas at
100.degree. C., preferably in the range from 200 mPas to 40,000
mPas and more particularly in the range from 300 mPas to 10,000
mPas, as measured by ASTM D 3236-88.
With combinations such as these, the melt viscosities,
crystallization behavior, cohesion and tackiness of the graft
copolymers can be controlled as required.
The ethylene oxide content of the copolymers should be at least 50%
by weight and is preferably at least 75% by weight.
The olefinically unsaturated monomers used for the purposes of the
invention are used in quantities of 95 to 20% by weight, based on
the total weight of the graft copolymer, preferably in quantities
of 90 to 30% by weight and more particularly in quantities of 80 to
60% by weight.
In a particularly preferred embodiment, graft copolymer (A) is
obtainable by reaction of a) 30 to 90% by weight of olefinically
unsaturated monomer with b) 10 to 70% by weight polyalkylene oxide
with a molecular weight of 400 to 50,000 g/mol, c) the ethylene
oxide content of the polyalkylene oxide being at least 50% by
weight.
The olefinically unsaturated monomers are selected from the group
of i) vinyl esters of linear aliphatic carboxylic acids or branched
aliphatic, araliphatic or cycloaliphatic carboxylic acids, ii)
esters of acrylic acid and/or methacrylic acid with linear or
branched aliphatic, araliphatic or cycloaliphatic alcohols, iii)
mono- or diesters of unsaturated aliphatic dicarboxylic acids with
linear or branched, aliphatic, araliphatic or cycloaliphatic
alcohols.
Suitable olefinically unsaturated monomers are vinylesters of
linear aliphatic carboxylic acids or branched aliphatic or
cycloaliphatic carboxylic acids. Carboxylic acids containing 2 to
22 carbon atoms and more particularly 2 to 12 carbon atoms are
preferred. Examples include vinyl acetate, vinyl propionate, vinyl
laurate and/or vinyl versatate.
Other suitable olefinically unsaturated monomers are esters of
acrylic acid with linear or branched aliphatic, araliphatic or
cycloaliphatic alcohols. Preferred alcohols contain 1 to 22 carbon
atoms, for example methyl acrylate, ethyl acrylate, butyl acrylate,
hexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate,
behenyl acrylate, tetrahydrofurfuryl acrylate, phenoxyethyl
acrylate, dicyclopentadienyl acrylate. However, (meth)acrylamides
are also suitable.
Instead of the esters of acrylic acid, corresponding esters of
other monocarboxylic acids, for example methacrylic acid, crotonic
acid or cinnamic acid, may also be used.
Other monomers are derived from mono- or diesters of unsaturated
aliphatic dicarboxylic acids with linear or branched aliphatic,
araliphatic or cycloaliphatic alcohols. Alcohols with a C chain
length of 1 to 22 carbon atoms are preferred. Examples of such
dicarboxylic acids are fumaric acid, maleic acid, citraconic acid
and itaconic acid. Examples of dicarboxylic acid monoesters are
monomethyl fumarate, monobutyl fumarate, monomethyl maleate,
monoethyl maleate, monobutyl maleate, monooctyl maleate, monolauryl
maleate, monostearyl maleate. Examples of dicarboxylic acid
diesters are dimethyl fumarate, dibutyl fumarate, dioctyl fumarate,
dilauryl fumarate, dimethyl itaconate, diethyl itaconate, dibutyl
itaconate, dimethyl maleate, diethyl maleate, dibutyl maleate,
dioctyl maleate, dilauryl maleate, distearyl maleate, dimethyl
citraconate, dibutyl citraconate, dioctyl citraconate.
Other monomers are acrylonitrile, styrene and
.alpha.-methylstyrene. The preferred monomer is vinyl acetate. The
above-mentioned monomers may be used individually or in the form of
mixtures. In such cases, mixtures with vinyl acetate are preferred
and the other monomers are typically used in quantities of at most
up to 50% by weight, preferably up to 20% by weight, more
preferably up to 10% by weight and most preferably up to 5% by
weight, based on the graft copolymer. Mixtures of vinyl acetate
with long-chain monomers are particularly suitable. The following
binary combinations in particular are mentioned in this regard:
vinyl acetate with vinyl laurate, vinyl acetate with vinyl
versatate, vinyl acetate with lauryl acrylate, vinyl acetate with
lauryl methacrylate, vinyl acetate with dibutyl maleate, vinyl
acetate with dibutyl itaconate or vinyl acetate with dibutyl
fumarate. These mixtures provide the graft copolymers with
particular tackiness. Accordingly, preferred olefinically
unsaturated monomers are mixtures of vinyl acetate with vinyl
laurate, vinyl versatate, lauryl acrylate, lauryl methacrylate,
dibutyl maleate, dibutyl itaconate or dibutyl fumarate, the
percentage content of vinyl acetate in the mixture being from 44%
by weight to 98% by weight.
A particularly preferred embodiment is characterized by the use of
mixtures of vinyl acetate with vinyl laurate in which the vinyl
laurate is present in a quantity of at most up to 50% by weight,
preferably up to 20% by weight, more preferably up to 10% by weight
and most preferably up to 5% by weight, based on the graft
copolymer.
Vinyl monomers containing polar groups are also suitable, including
for example N-vinyl pyrrolidone, N-vinyl caprolactam, vinyl
sulfonates (for example sodium vinyl sulfonate), vinyl
phosphonates, N-vinyl formamides, N-vinyl acetamides, hydroxyethyl
acrylate, hydroxypropyl acrylates, monoacrylates of polyalkylene
glycols; acrylic acid esters or acrylic acid amides containing
amine groups and the analogous methacrylic acid derivatives are
also suitable.
Mixtures of these polar monomers with one another are also
suitable. They are normally used in combination with the monomers
mentioned above. These polar monomers are typically used in
quantities of at most up to 50% by weight, preferably up to 20% by
weight, more preferably up to 10% by weight and most preferably up
to 5% by weight, based on the graft polymer.
Monomers containing acid groups may also be used in order to
improve alkali solubility. They are normally used in combination
with the monomers mentioned above. The monomers containing aid
groups may be selected, for example, from acrylic acid, methacrylic
acid, fumaric acid, maleic acid, crotonic acid, itaconic acid,
citraconic acid or cinnamic acid. The anhydrides of the
dicarboxylic acids mentioned above may also be used. These monomers
are typically used in quantities of at most up to 50% by weight,
preferably up to 20% by weight, more preferably up to 10% by weight
and most preferably up to 5% by weight, based on the graft
polymer.
One particular embodiment of the invention is a water-soluble or
water-dispersible hotmelt adhesive based on at least one
water-soluble, water-dispersible or alkali-soluble polymer prepared
by graft copolymerization of olefinically unsaturated monomers onto
polyalkylene oxides as component (A), at least one olefinically
unsaturated monomer from the group of a) esters of crotonic acid,
cinnamic acid, mono- or di-esters of fumaric acid, maleic acid,
citraconic acid or itaconic acid or from the group of b) vinyl
esters, acrylates or methacrylates corresponding to general formula
(I) and/or (II): CH.sub.2.dbd.CH--O--C(O)--R.sub.1 with
R.sub.1=C.sub.11-21 (I) CH.sub.2.dbd.CR.sub.2--C(O)--O--R.sub.3
with R.sub.2=H, CH.sub.3 and R.sub.3=C.sub.12-22 (II) being used
and being present in the graft copolymer in a quantity of 5 to 50%
by weight.
Suitable polymerization initiators are, above all, organic
peroxides, such as diacetyl peroxide, dibenzoyl peroxide,
di-tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butyl
perpivalate, succinyl peroxide, tert.butyl permaleate, tert-butyl
hydroperoxide, cumene hydroperoxide, di-tert-amyl peroxide,
tert-butyl peracetate, tert-butyl perisobutyrate, dilauroyl
peroxide, dioctanoyl peroxide, diisopropyl peroxydicarbamate,
didecanoyl peroxide, bis-(o-tolyl)-peroxide. Mixtures of the
initiators mentioned, redox initiators or azo initiators are also
suitable.
The water-soluble or water-dispersible hotmelt adhesive according
to the invention contains 0 to 70% by weight of at least one
polymer from the group of polyesters, polyurethanes, alkyl
polyacrylates or polymethacrylates, acrylic acid homopolymers
and/or copolymers and/or vinyl polymers as component (B).
One particular embodiment of the invention is a water-soluble or
water-dispersible hotmelt adhesive based on at least one
water-soluble, water-dispersible or alkali-soluble polymer prepared
by graft copolymerization of olefinically unsaturated monomers onto
polyalkylene oxides as component (A), characterized in that the
hotmelt adhesive contains: A) 20 to 80% by weight of component (A),
B) 1 to 70% by weight of at least one polymer from the group of
polyesters, polyurethanes, alkyl poly(meth)acrylates, acrylic acid
homopolymers and/or copolymers and/or vinyl polymers, C) 10 to 70%
by weight of at least one resin, D) 0 to 30% by weight of at least
one plasticizer, F) 0 to 3% by weight of at least one typical
auxiliary and additive, the sum total of the components being 100%
by weight.
In a preferred embodiment, the hotmelt adhesive according to the
invention contains: B1) as component (B1), 10 to 50% by weight of a
(meth)acrylic acid homopolymer and/or copolymer and/or B2) as
component (B2), 5 to 30% by weight of a saturated and/or
unsaturated polyester and/or B3) at least one alkyl
poly(meth)acrylate as component (B3), the alkyl group having a
chain length of 1 to 18 carbon atoms, and/or B4) as component (B4),
a polyvinyl alcohol with a molecular weight above 1,000 g/mol
and/or a polyvinyl alkylether containing 1 to 14 carbon atoms in
the alkyl group and/or B5) as component (B5), 5 to 30% by weight of
a polyurethane.
Component (B) preferably contains at least one (meth)acrylic acid
homopolymer and/or copolymer; styrene, methylstyrene and/or other
alkylstyrenes and .alpha.-olefins may be used as comonomer. The at
least one (meth)acrylic acid homopolymer and/or
copolymer--component (B1)--may be present in the hotmelt adhesive
according to the invention in a quantity of 10 to 50% by weight,
preferably 5 to 35% by weight and more particularly 10 to 30% by
weight.
In a preferred embodiment, at least one polyester is present in
component (B) as component (B2). The polyester (B2) is preferably a
saturated and/or unsaturated polyester. Preferred polyesters are
based on aromatic dicarboxylic acids, such as phthalic acid or
terephthalic acid, with at least one polyol from the group
consisting of neopentyl glycol, glycerol or pentaerythritol. The
esters based on aromatic dicarboxylic acids containing sulfo groups
disclosed in EP 0737233 are particularly preferred.
Component (B2) is present in the hotmelt adhesive according to the
invention in a quantity of 5 to 30% by weight and preferably in a
quantity of 8 to 25% by weight.
In a preferred embodiment, component (B) contains at least one
alkyl poly(meth)acrylate as component (B3). The alkyl group
preferably has a chain length of 1 to 18 carbon atoms and, more
particularly, 1 to 4 carbon atoms.
Component (B3) is present in the hotmelt adhesive according to the
invention in a quantity of 5 to 40% by weight and preferably 8 to
20% by weight.
In a preferred embodiment, component (B) contains at least one
vinyl polymer as component (B4). The preferred group of vinyl
polymers includes, for example, polyvinyl alcohol with a molecular
weight above 1,000 g/mol, polyvinyl pyrrolidone, vinyl
pyrrolidone/vinyl acetate copolymers, polyvinyl ethers, more
particularly polyvinyl alkylethers containing 1 to 4 carbon atoms
in the alkyl group, for example polyvinyl methylether or polyvinyl
ethylether.
Component (B4) is present in the hotmelt adhesive according to the
invention in a quantity of 5 to 40% by weight and preferably in a
quantity of 8 to 20% by weight.
In a preferred embodiment, component (B) contains at least one
polyurethane as component (B5). The polyurethanes used contain at
least one terminal OH group and have a molecular weight of 2,000
g/mol to 100,000 g/mol and preferably in the range from 10,000
g/mol to 70,000 g/mol. Component (B5) has a melt viscosity of up to
200,000 mPas at 190.degree. C. and a softening range of 50 to
70.degree. C.
The hotmelt adhesive according to the invention contains a resin as
component (C). The resin provides for additional tackiness and
improves the compatibility of the hotmelt adhesive components. It
is used in a quantity of 10 to 70% by weight. The resin is selected
from a) hydroabietyl alcohol and esters thereof, more especially
esters with aromatic carboxylic acids, such as terephthalic acid
and phthalic acid, b) preferably modified natural resins, such as
resinic acids of balsam resin, tallol resin or wood rosin, for
example fully saponified balsam resin or alkyl esters of optionally
partly hydrogenated rosin with low softening points, for example
methyl, diethylene glycol, glycerol and pentaerythritol esters, c)
SMA resins (copolymers of styrene and maleic anhydride), d) acrylic
acid copolymers, preferably styrene/acrylic acid copolymers, and e)
resins based on functional hydrocarbon resins.
An alkyl ester of partly hydrogenated rosin--the alkyl group
preferably containing 1 to 6 carbon atoms--may also be used as the
tackifying resin.
Acrylic acid copolymers are preferably used.
The plasticizer, component (D), is preferably used to adjust
viscosity and is generally present in the hotmelt adhesive
according to the invention in a concentration of 0 to 30% by weight
and preferably in a concentration of 5 to 30% by weight. Suitable
plasticizers are monohydric or polyhydric alcohols, preferably
glycol monophenyl ether, hexamethylene glycol, glycerol and, in
particular, polyalkylene glycols with a molecular weight of 200 to
6,000. Polyethylene glycols with a molecular weight of up to about
1,000 and preferably up to about 600 and esterified or etherified
derivatives thereof are preferred. Polypropylene glycol,
polybutylene glycol and polymethylene glycol are also suitable.
Esters, for example liquid polyesters and glycerol esters, such as
glycerol diacetate and glycerol triacetate, and neopentyl glycol
dibenzoate, glyceryl tribenzoate, pentaerythritol tetrabenzoate and
1,4-cyclohexane dimethanol dibenzoate, are preferably used as the
plasticizers. Finally, alkyl monoamines and fatty acids preferably
containing 8 to 36 carbon atoms may also be used.
Plasticizers based on aromatic dicarboxylic acid esters, i.e., the
corresponding ester of phthalic acid, isophthalic acid or
terephthalic acid, are preferably used. The alcohol component of
these esters used as plasticizers normally contains 1 to 8 carbon
atoms.
Other suitable plasticizers are alkyl monoamines and fatty acids;
alkyl monoamines and fatty acids containing 8 to 36 carbon atoms
are preferred.
Suitable plasticizers are, above all, medicinal white spirit and
naphthenic mineral oils.
In a preferred embodiment, the hotmelt adhesive according to the
invention contains A) 20 to 80% by weight of at least one graft
copolymer, B) 5 to 20% by weight of at least one saturated and/or
unsaturated polyester as component (B2), C) 10 to 70% by weight of
at least one acrylic acid copolymer as component (C), D) 5 to 25%
by weight of at least one plasticizer based on polyalkylene glycol
with a molecular weight of 200 to 6,000 g/mol as component (D), the
sum total of the components being 100% by weight.
In addition, typical auxiliaries and additives--component (E)--may
be incorporated in the hotmelt adhesive according to the invention.
These include, above all, stabilizers. The function of stabilizers
is to prevent the reactive monomers from entering into an unwanted
or premature reaction and to protect the polymers against
decomposition during processing. Such stabilizers are, in
particular, antioxidants. They are added to the hotmelt adhesive in
quantities of typically up to 3% by weight and preferably about 0.1
to 1.0% by weight. Other auxiliaries and additives are pigments,
more particularly TiO.sub.2.
The hotmelt adhesive according to the invention is used for bonding
substrates by application in the form of a melt and by setting on
cooling to room temperature (=hotmelt adhesive). The hotmelt
adhesive according to the invention is generally solid at
20.degree. C. and free from solvents which would be troublesome
during application from the melt.
The hotmelt adhesive according to the invention is generally
prepared by mixing the components. To this end, optionally a
polymer from the group of polyesters, polyurethanes, alkyl
poly(meth)acrylates, acrylic acid homo- and/or copolymers and/or
vinyl polymers (component B), optionally a resin (component C),
optionally plasticizers (component D) and optionally at least one
of the usual auxiliaries and additives (component E) are mixed at
120 to 180.degree. C. and more particularly at ca. 140.degree. C.
to form a homogeneous melt. The graft copolymer (component A) is
then added, followed by stirring to homogeneity. After the
completely homogenized composition has been packed in suitable
containers, it is left to cool, solidifying in the process. It is
now ready for use. The melt could of course also be directly
applied to a substrate without cooling and thus directly used for
bonding without a cooling phase.
However, like other commercially available hotmelt adhesives, the
hotmelt adhesive according to the invention is melted before use
and then applied to the substrate to be bonded.
The hotmelt adhesives according to the invention are used to bond
substrates of which at least one is to be re-used. The substrates
are such materials as glass, metal, lacquered or unlacquered paper
or corresponding paperboards and, above all, plastics, for example
PET, PEN, PP, PVC, PS and PE. Containers or films, for example, may
be produced from such materials. In a particular embodiment of the
invention, the substrates to be bonded are, on the one hand,
containers and, on the other hand, labels.
Examples of containers include bottles, cans, drums, tubes or
cartridges. They consist essentially of optionally plated or
galvanized metal, for example tin plate or aluminum, glass or
thermoplastics, such as polyethylene terephthalate, polycarbonate,
polyethylene, polypropylene, polyvinyl chloride or polystyrene. A
polar plastic, more particularly a polyester, is preferably used.
Corresponding hollow containers are used in particular for mineral
waters and refreshing drinks.
The labels consist on the one hand of thermoplastics, such as
polyethylene, polypropylene, polystyrene, polyvinyl chloride or
cellophane. It is preferred to use labels of a film based on
nonpolar plastics, more particularly oriented polypropylene (OPP).
However, the labels may also be based on paper, optionally in
combination with a polymer. Depending on the material and the
production process, the following labels, for example, may be used:
simple labels of nonfinished paper, labels of surface-finished
paper, high-gloss labels of cast-coated label papers, labels of
papers coated with aluminum by vapor deposition and labels of
aluminum-lined papers. The shape of the labels does not have to
meet any particular requirements. Wrap-around labels and shield
labels, for example, may be used.
A specific application of the hotmelt adhesive according to the
invention is the labeling of re-usable materials, more particularly
hollow containers of PET labeled with paper or plastic labels.
In the process of labeling with hotmelt adhesives, a pickup
adhesive is normally applied to the label or to the hollow
container. The label is fixed on the hollow container by the pickup
adhesive and is normally in the form of a wrap-around label. An
overlap adhesive is applied to the end of the label by rollers or
comparable application systems. The hotmelt adhesive according to
the invention may be used both as a pickup adhesive and as an
overlap adhesive. This simplifies the labelling process. For
example, there is no need for a second melting tank.
By virtue of the balanced ratio of cohesion to adhesion, the
hotmelt adhesive according to the invention has very good pickup
properties, particularly in high-performance labeling machines
where up to 50,000 hollow containers per hour are labeled. In other
words, both the pickup of the labels and their application to
corresponding hollow containers take place smoothly. In addition,
in high-performance labeling machines, the hotmelt adhesive
according to the invention is distinguished by good machine running
properties, i.e., it does not string and causes minimal, if any,
soiling.
Where plastic labels in particular are used, low processing
temperatures are necessary. The processing temperatures are in the
range from 70.degree. C. to 150.degree. C. and preferably in the
range from 90.degree. C. to 140.degree. C.
For problem-free processing, the adhesives used must have a
suitably low viscosity. The hotmelt adhesives according to the
invention have a Brookfield viscosity, as measured to ASTM D
3236-88, in the range from 200 mPas to 2,500 mPas, preferably in
the range from 400 mPas to 1,500 mPas and more particularly in the
range from 600 mPas to 1,000 mPas at 150.degree. C. Their low
viscosity enables the hotmelt adhesives according to the invention
to be applied by roller application systems (for example Krones
Canmatic), segment application systems (for example Kones
Contiroll) or--given a suitable formulation--by commercially
available nozzle systems (for example Nordson).
The water-soluble or water-dispersible hotmelt adhesives according
to the invention are used quite generally for applications where
bonded articles or bonds are disintegrated in water or aqueous
media. Such applications include sanitary articles, for example
diapers or lavatory paper, or articles used in packaging. In the
packaging field, the invention may be used in particular in
labeling, in the closure of boxes and in bookbinding.
Another specific application of the hotmelt adhesives according to
the invention is the labeling of PET hollow containers which are to
be re-used after use (re-usable systems) or recycled. The hotmelt
adhesives according to the invention are suitable both for old
recycling systems and for more recent systems (WO 95/29952 of
United Resource Recovery Corporation).
In the recycling processes originally used, the hollow containers
labeled with hotmelt adhesives are sorted according to type,
size-reduced and then washed in an energy-intensive and laborious
washing process in water and alkali baths. All soils (including
adhesive) have to be removed as far as possible from the PET in
order to guarantee high purity and hence re-usability for PET
containers (possibly even for foods) with a high recycle content
(up to 30%).
Washing alkali concentrations of 2% and temperatures of 90.degree.
C. are typical of the washing process. The residence time may be up
to 20 minutes.
The hotmelt adhesives according to the invention are readily
soluble both in cold water and in warm water. The residence time
can thus be reduced to 10 minutes, the washing alkali concentration
to 1% and the washing temperature to 40 50.degree. C. At room
temperature, the residence time in a 1% washing alkali is 10 to 15
minutes.
By using the hotmelt adhesives according to the invention, good
separation from the useful materials is achieved in the alkaline
medium (typically 0.5 to 2% NaOH solution) or in water. In
addition, the adhesive is effectively prevented from
re-accumulating in the form of so-called stickies on the useful
material or in the recycling plants. Even if the hotmelt adhesive
according to the invention is pressure-sensitive, it is
"detackified" in the alkaline medium and does not re-accumulate on
the useful material or in the recycling plants. In the particular
case of bonds with hollow containers of recyclable material which
are intended to have high resistance to frozen water or
condensation, the necessary insolubility in water, but complete
solubility or dispersion in the alkaline medium in alkalis can be
achieved by suitable formulations.
However, all the hotmelt adhesives according to the invention can
readily be removed in the described recycling process.
However, the process according to the invention involving the
hotmelt adhesives according to the invention not only provides for
relatively mild washing conditions, the recycled PCT is also of
high quality and can be re-used in new bottles to a greater extent
than otherwise usual (>50%).
In addition, the hotmelt adhesives according to the invention are
also particularly suitable for more recent recycling systems as
disclosed, for example, in WO 95/29952. In this way, 100% re-use of
the container material can be guaranteed, even for food packs. The
size-reduced polyester plastics, preferably PET, are first washed
in alkali, after which the polyester plastic is converted into its
salts in an alkaline atmosphere. By virtue of the water-soluble,
water-dispersible or alkali-soluble properties of the hotmelt
adhesives according to the invention, the adhesive is, ideally, not
introduced at all into the second process step. Any minimal
residues of the adhesive there still may be, however, are reacted
to form volatile gases as described in WO 95/29952 and may then
readily be removed.
The invention is illustrated by the following Examples.
EXAMPLES
I Production and Properties of the Graft Copolymers
1. Starting Components
TABLE-US-00001 LIPOXOL 4000 Polyethylene glycol 4000 from Huls TBPB
t-Butyl peroxybenzoate from Peroxid-Chemie LUCIDOL CH 50X Dibenzoyl
peroxide from Akzo IRGANOX 1010 Phenolic antioxidant from Ciba
Spezialitatenchemie BREOX 75W Statistical ethylene oxide/propylene
oxide 18000 copolymer from International Speciality Chemicals Vac
Vinyl acetate VEOVA 10 Vinyl versatate from Shell VL Vinyl laurate
LA Lauryl acrylate DBM Dibutyl maleate
2. Examples
Example 1
100 g LIPOXOL 4000 were introduced into a 1-liter four-necked flask
equipped with a stirrer, thermometer, nitrogen inlet, dropping
funnel, reflux condenser and heating bath and were melted at a bath
temperature of 90.degree. C. 15 g vinyl acetate, 0.7 g TBPB and 0.3
g LUCIDOL CH 50.times. dissolved in 3.4 g ethyl acetate were then
added. 385 g vinyl acetate were then added dropwise over a period
of 5 hours at that temperature. After the dropwise addition, the
mixture was stirred for 1 hour at a bath temperature of 90.degree.
C. The reflux condenser was then replaced by a descending
condenser, the reaction mixture was heated to 160.degree. C. and
volatile constituents were distilled off over a period of 45
minutes. 2 g IRGANOX 1010 were then added and the whole was
degassed for another 20 minutes at 160.degree. C. in a vacuum of 15
mbar. A light yellow reaction product with a melt viscosity of
12,000 mPas at 150.degree. C. was obtained.
Example 2
The procedure was as in Example 1, except that polyethylene glycol
4000 was replaced by polyethylene glycol 1500. A light yellow
reaction product with a melt viscosity of 4,200 mPas at 150.degree.
C. was obtained.
Examples 3 to 8 (see Table 1)
The batch size of the following Examples was 500 g.
The polyalkylene oxide was introduced into the apparatus described
in Example 1 and was melted at a bath temperature of 90.degree. C.
15 g vinyl acetate and the initiator were then added. The remaining
quantity of monomer was then added dropwise over the periods shown
in the Table. After the addition, the mixture was left to react for
the periods indicated at a bath temperature of 90.degree. C. The
reflux condenser was then replaced by a descending condenser, the
reaction mixture was heated to 160.degree. C. and volatile
constituents were distilled off over a period of 45 minutes. 2.5 g
IRGANOX 1010 were then added and the mixture was degassed for
another 20 minutes at 160.degree. C. in a vacuum of 15 mbar.
TABLE-US-00002 TABLE 1 Example 3 4 5 6 7 8 Polyalkylene oxide PEG
PEG PEG PEG PEG PEG [ratio by weight] 4000 4000 6000 12000 20000
20000 Monomer [ratio Vac Vac Vac VAc VAc VAc by weight] Ratio by
weight of 50:50 30:70 40:60 30:70 50:50 70:30 polyalkylene oxide to
monomer Quantity of 250 350 300 350 250 150 monomer [g] Monomer
addition 02:40 03:42 01:40 05:20 03:23 02:14 time [hours:mins.]
After-reaction 01:15 02:55 01:30 03:10 02:30 01:25 [hours:mins.]
Initiator [% by 0.075 0.075 0.075 0.075 0.075 0.075 weight based on
DBP*) + DBP*) + DBP*) + DBP*) + DBP*) + DBP*) + monomer] 0.175
0.175 0.175 0.175 0.175 0.175 TBPB TBPB TBPB TBPB TBPB TBPB
Viscosity 1,280 at 14,400 at 15,360 at 20,640 at 18,560 at 9,600 at
[mPa s] 100.degree. C. 100.degree. C. 100.degree. C. 150.degree. C.
150.degree. C. 150.degree. C. *)LUCIDOL CH 50X
Examples 9 to 11 (Table 2)
The batch size of the following Examples was 500 g.
The polyalkylene oxide was introduced into the apparatus described
in Example 1 and was melted at a bath temperature of 90.degree. C.
15 g of the monomer mixture shown in Table 2 and the initiator were
then added. The remaining quantity of monomer was then added
dropwise over the periods shown in Table 2. After the addition, the
mixture was left to react for the periods indicated at a bath
temperature of 90.degree. C. The reflux condenser was then replaced
by a descending condenser, the reaction mixture was heated to
160.degree. C. and volatile constituents were distilled off over a
period of 45 minutes. 2.5 g IRGANOX 1010 were then added and the
mixture was degassed for another 20 minutes at 160.degree. C. in a
vacuum of 15 mbar.
TABLE-US-00003 TABLE 2 Example 9 10 11 Polyalkylene oxide PEG 4000
PEG 4000 PEG 4000 [ratio by weight] Monomer [ratio by Vac + VAc +
Vac + weight] VEOVA 10 BuA [5:2] DBM [5:2] [5:2] Ratio by weight of
30:70 30:70 30:70 polyalkylene oxide to monomer Quantity of monomer
350 350 350 [g] Monomer addition 3:30 6:30 6:15 time [hours:mins.]
After-reaction 01:30 03:00 06:00 [hours:mins.] Initiator [% by
weight 0.113 DBP*) + 0.075 DBP*) + 0.075 DBP*) + based on monomer]
0.175 0.175 0.175 t-BPB t-BPB t-BPB Viscosity [mPa s] 15,100 at
13,700 at 11,200 at 100.degree. C. 100.degree. C. 100.degree. C.
*)LUCIDOL CH 50X
Example 12
80 g LIPOXOL 4000 were introduced into a 1-liter four-necked flask
equipped with a stirrer, thermometer, nitrogen inlet, dropping
funnel, reflux condenser and heating bath and were melted at a bath
temperature of 90.degree. C. 5 g vinyl acetate, 0.49 g TBPB and
0.21 g LUCIDOL CH 50.times. dissolved in 2.59 g ethyl acetate were
then added. 275 g vinyl acetate were then added dropwise over a
period of 5 hours at 95.degree. C. After the dropwise addition, the
mixture was stirred for 1 hour at an internal temperature of
100.degree. C. 40 g crotonic acid, 0.1 g TBPB and 0.03 g LUCIDOL
dissolved in 0.37 g ethyl acetate were then added and the whole was
stirred for 1 hour at 100.degree. C. The reflux condenser was then
replaced by a descending condenser, the reaction mixture was heated
to 160.degree. C. and volatile constituents were distilled off over
a period of 45 minutes. 1 g BHT was then added and the whole was
degassed for another 20 minutes at 160.degree. C. in a vacuum of 15
mbar. A light yellow reaction product with a melt viscosity of
3,400 mPas at 150.degree. C. was obtained.
Example 13
A mixture of 125 g polyethylene glycol 12000 and 75 g BREOX 75W
18000 was introduced into a 1-liter four-necked flask equipped with
a stirrer, thermometer, nitrogen inlet, dropping funnel, reflux
condenser and heating bath and was melted at a bath temperature of
90.degree. C. 15 g vinyl acetate, 0.53 g TBPB and 0.45 g LUCIDOL CH
50.times. dissolved in 3.55 g ethyl acetate were then added. 285 g
vinyl acetate were then added dropwise over a period of 5 hours at
an internal temperature of 85.degree. C. After the dropwise
addition, the mixture was stirred for 1.5 hours at a bath
temperature of 90.degree. C. The reflux condenser was then replaced
by a descending condenser, the reaction mixture was heated to
160.degree. C. and volatile constituents were distilled off over a
period of 45 minutes. 2 g IRGANOX 1010 were then added and the
whole was degassed for another 20 minutes at 160.degree. C. in a
vacuum of 15 mbar. A light yellow reaction product with a melt
viscosity of 7,000 mPas at 150.degree. C. was obtained.
Example 14
120 g polyethylene glycol 12000 were introduced into a 1-liter
four-necked flask equipped with a stirrer, thermometer, nitrogen
inlet, dropping funnel, reflux condenser and heating bath and were
melted at a bath temperature of 90.degree. C. A mixture of 260 g
vinyl acetate, 20 g vinyl laurate and 14 g of a 5.85% by weight
solution of LUCIDOL CH 50.times. in ethyl acetate was then added
dropwise over a period of 5 hours. After the dropwise addition, the
mixture was left to react for 30 mins. at a bath temperature of
90.degree. C. 0.49 g tert-butyl peroxybenzoate was then added and
the mixture was stirred for 1 hour at 125.degree. C. The reflux
condenser was then replaced by a descending condenser, the reaction
mixture was heated to 160.degree. C. and volatile constituents were
distilled off over a period of 40 minutes. 2 g IRGANOX 1010 were
then added and the whole was degassed for another 20 minutes at
160.degree. C. in a vacuum of 15 mbar. A light yellow reaction
product with a melt viscosity of 7,000 mPas at 150.degree. C. was
obtained.
Examples 15 to 20 (Table 3)
The batch size of the following Examples was 500 g.
The polyalkylene oxides mentioned below were reacted with the
monomers as in Example 14. The results are set out in Table 3.
TABLE-US-00004 TABLE 3 Example 15 16 17 18 19 20 Polyalkylene oxide
PEG 600 PEG 12000 PEG 12000 PEG 6000 + PEG 12000 + PEG 12000 +
[ratio by weight] BREOX 75W BREOX 75W PEG 600 18000 18000 [10:10]
[2.5:1.5] [2.5:1.5] Monomer [ratio Vac Vac + VL Vac + LA VAc + VL
VAc + VL VAc by weight] [5:2] [5:1] [5:1] [5:1] Ratio by weight of
20:80 30:70 30:70 40:60 40:60 20:80 polyalkylene oxide to monomer
Quantity of 400 350 350 300.00 300.00 350.00 monomer [g] Monomer
addition 5:00 3:30 3:40 2:45 2:40 4:15 time [hours:mins.]
After-reaction 1:30 1:30 1:30 1:30 1:30 1:30 [hours:mins.]
Initiator [% by 0.293 DBP*) + 0.293 DBP*) + 0.293 DBP*) + 0.293
DBP*) + 0.293 DBP*) + 0.293 DBP*) + weight based on 0.175 TBPB
0.175 TBPB 0.175 TBPB 0.175 TBPB 0.175 TBPB 0.175 TBPB monomer]
Viscosity [mPa s] 8,300 at 3,500 at 7,400 at 1,300 at 4,300 at
5,400 at 100.degree. C. 100.degree. C. 100.degree. C. 150.degree.
C. 150.degree. C. 150.degree. C. *)LUCIDOL CH 50X
II. Production and Properties of the Hotmelt Adhesives 1. Starting
Components a) EASTMAN AQ 1045, a polyester from Eastman Chemical b)
Polyethylene glycol PEG 400 and PEG 600 from Clariant c) JONCRYL
682, acrylic acid copolymer from S.C. Johnson Polymer d) G-Cryl
5005, acrylic resin from Cognis Corporation e) PEARLBOND 501, a
polyurethane from Merquinsa f) ELVACITE 2978, a polyacrylate from
Ineos Acrylics g) ELVACITE 4026, a UV-reactive polyacrylate from
Ineos Acrylics h) K 4100, a polyacrylate from Belland 2. Production
of the Hotmelt Adhesives by Mixing
The formulations of the Examples (Table 4) were prepared by the
generally known method. To this end, the polyethylene glycol, the
resin and the polyester, the polyurethane or the polyacrylate were
mixed at 140.degree. C. in a laboratory stirrer until they appeared
visually homogeneous. The graft copolymer was then added and also
completely homogenized. This generally takes a total of ca. 60 to
120 mins. Depending on its composition, the melt is transparent,
opaque or hazy (the same also applies to the melt cooled to room
temperature). The melt mixture was packed in containers and then
cooled, solidifying in the process. After cooling, it was used for
various purposes according to its composition.
EXAMPLES
TABLE-US-00005 TABLE 4 (composition in % by weight) Example
Components 1 2 3 4 5 6 7 8 9 Graft copolymer of Example 16 25 -- --
41 62 -- -- -- -- Graft copolymer of Example 18 -- 30 35 -- -- --
-- -- -- Graft copolymer of Example 20 -- -- -- -- -- 41 41 41 41
PEG 400 15 5 20 12 -- 12 12 12 12 PEG 600 -- -- -- -- 8 -- -- -- --
JONCRYL 682 20 -- -- 35 20 35 35 35 35 G-Cryl 5005 30 65 25 -- --
-- -- -- -- EASTMAN AQ 1045 10 -- 20 12 10 -- -- -- -- PEARLBOND
501 -- -- -- -- -- 12 -- -- -- ELVACITE 2978 -- -- -- -- -- -- 12
-- -- ELVACITE 4026 -- -- -- -- -- -- -- 12 -- K4100 -- -- -- -- --
-- -- -- 12 Total 100 100 100 100 100 100 100 100 100
Example 22 of US patent application U.S. Pat. No. 3,891,584 was
copied for comparison. This Example contains a mixture of 75% of a
copolymer of PEG 4000 and vinyl acetate in a ratio of 35:65 and 25%
Nevillac soft.
4. Description of the Hotmelt Adhesives
Example 1
Pressure-sensitive low-viscosity hotmelt adhesive with a heat
resistance of ca. 80.degree. C. and a processing temperature of ca.
120.degree. C. The hotmelt adhesive may be used for labeling
aerosol cans, shaped bottles and beverage cans with subsequent
shrinkage of the labels, preferably based on OPP.
Example 2
Non-pressure-sensitive, granulatable hotmelt adhesive which is
particularly suitable for bonding highly lacquered paperboards and
papers and for the labeling of goods intended for prolonged storage
at ca. 60.degree. C.
Example 3
Hotmelt adhesive for labeling and coating films. Heat resistance
ca. 80.degree. C.
Example 4
Pressure-sensitive low-viscosity hotmelt adhesive for labeling
plastic bottles.
Example 5
Pressure-sensitive hotmelt adhesive for labeling goods using
commercially available nozzle systems (for example from
Nordson).
TABLE-US-00006 TABLE 5 Epprecht viscosity (cone D) Example
Appearance of melt 125.degree. C. 150.degree. C. 6 Dark brown;
clear 2.64 Pa s 0.92 Pa s 7 Light yellow; clear 7.04 Pa s 2.24 Pa s
8 Light yellow; clear 6.72 Pa s 2.00 Pa s 9 Light yellow 7.04 Pa s
2.27 Pa s
III Testing of the Hotmelt Adhesives 1. Labeling
In a Krones "Conti Roll" test labelling unit, the hotmelt adhesive
of Examples 1 to 9 was applied in strips to the beginning and end
of OPP labels in a quantity of 1.1 g/m.sup.2 (corresponding to a
quantity of 0.05 g/label) at a temperature of 140.degree. C. PET
bottles were labeled in this way.
IV Results
Solubility in Cold and Warm Water
The formulations of Examples 1 to 9 show good and rapid removal of
the adhesive from plastic surfaces, for example, plastic surfaces
of polyethylene terephthalate (PET). The adhesive removed is
present in the form of a fine-particle dispersion in water. By
comparison, the formulation from U.S. Pat. No. 3,891,584 (Example
22) is very coarsely dispersed in water.
Alkali Solubility:
The formulations of Examples 1 to 9 show very good alkali
solubility. The comparison formulation of Example 22 of U.S. Pat.
No. 3,891,584 forms a coarse dispersion with even residues of the
adhesive remaining on the test specimen.
Polyrecycling Method:
The hotmelt adhesives of Examples 1 to 8 show a removal of more
than 98% in the Polyrecycling method and may therefore be
classified as good. The comparison from U.S. Pat. No. 3,891,584
(Example 22) shows a removal of ca. 45% which would have to be
classified as unacceptable.
Containers Containing Carbon Dioxide:
All the hotmelt adhesives of Examples 1 to 9 show good adhesion of
plastic labels to plastic surfaces and have the required
flexibility when it comes to filling with liquids containing carbon
dioxide and storage.
V Description of the Test Methods
Melt viscosity: Brookfield Model PVT DV II, 150.degree. C., spindle
27; by ASTM D 3236-88 Epprecht viscosity, Cone D, ICI viscosimeter,
by DIN 53229 Softening point by DIN 52011 (ring/ball method)
Stringing: a glass rod is introduced into the hotmelt adhesive
melted at ca. 160.degree. C. and slowly withdrawn and the
Theological behavior of the hotmelt adhesive is visually evaluated.
Evaluation includes the manner in which the molten adhesive drips
off the glass rod and the formation of adhesive threads during
withdrawal of the glass rod from the adhesive melt. Heat
resistance: the labeled containers are stored in a drying cabinet
for 14 days at increasing temperatures. The adhesion quality of the
overlap and pickup bonds is then evaluated. The heat resistance
value is the maximum temperature at which storage is still possible
without any loss of bond quality. Polyrecycling: method of
Polyrecycling AG (CH-8570 Weinfelsen). Determination of solubility
in cold water and warm water: Solubility in cold water is
determined at 25.degree. C.; solubility in warm water at 60.degree.
C. This method is used for laminates containing up to 3% adhesive.
The test specimens are prepared to the specification of
Polyrecycling AG (Polyrecycling method, see above). Alkali
solubility: Alkali solubility is tested at 60.degree. C. in 1.5%
caustic soda. This method is used for laminates containing up to 3%
adhesive. The test specimens are prepared to the specification of
Polyrecycling AG (Polyrecycling method, see above).
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